A universal joint is assembled between shafts typically to deliver torque through an angle. Examples of use of universal joints are in shafts connecting automotive steering columns to the steering gear, drive shafts for automobiles, trucks and vehicles and shafts used in industrial machines, off road equipment, airplanes, etc. Because the shafts rotate and typically define an angle at the universal joint, there is continuous relative motion between the crosspiece or spider of the universal joint and the yokes on the shafts or parts joined to the crosspiece or spider of the universal joint.
A universal joint is a structure well-known in the art. A main element of the universal joint is a crosspiece, also called a connector or spider. The crosspiece has respective pairs of trunnions which project radially out in opposite directions from the axis of the crosspiece. Each shaft end or part to be joined at the universal joint has a yoke to be connected to the crosspiece. Each yoke includes a pair of spaced apart arms each attached at one of a pair of opposite trunnions. Each arm of each yoke receives a respective projecting trunnion. The yoke arm has an opening that receives the trunnion.
If there is a bend in the shaft at the joint, as the shaft rotates, the bend is accommodated by each yoke arm moving circumferentially around its trunnion as the shaft including the joint is rotated. To accommodate such motion, a radial bearing is disposed between the exterior of the trunnion and the interior of the trunnion receiving opening in the yoke arm. That opening for the trunnion is typically defined by a cup installed in the yoke arm. The radial bearing is disposed between the exterior of the trunnion and the interior of the cup. The radial bearing is typically a needle bearing comprised of a circumferential array of axially extending needle rollers, which are thin, elongate cylindrical rollers. Typically, the bearing is received in the trunnion supporting cup disposed in the opening of the yoke arm, and the bearing rotates with respect to the exterior of the trunnion and the interior of the cup.
The cup for the trunnion is open at the end into which the trunnion is installed and is usually closed at the outer distal end beyond the end of the trunnion and beyond the radial or needle bearing. When the needle bearing is installed in the cup, the needles typically do not extend to the closed end of the cup. Between the outer distal ends of the bearing needles and the closed end of the cup, there may be a needle roller spacer which would support the outer ends of the needles.
In some applications of trunnions and cups for a universal joint, there is a thrust washer at the outer end of the cup, outward of the trunnion, which acts as a thrust and wear surface that bears axial loads applied by the outer trunnion face of the universal joint crosspiece or spider. In a universal joint having a thrust washer and a needle roller spacer, the needle roller spacer is shaped and sized to ensure that the needle rollers do not overhang the trunnion corner breaks or the distal outer peripheral edge of the trunnion. Integrated thrust washer and needle roller spacer configurations are known in many universal joint applications. For example, such integral, one-piece arrangements are suggested in U.S. Pat. Nos. 4,050,130 and 4,317,341.
In other applications, it may be desirable to have the thrust washer and needle roller spacer present in the trunnion cup be separate to operate as separate components. Providing separate thrust washer and needle roller spacer components may pose a problem during the bearing assembly process and during assembly of the bearing into the universal joints. During the bearing assembly process, there are normal vibration and shaking in the process and there is unpredictable manual handling which can create individual displacements of the thrust washer and the needle roller spacer. These displacements may include the thrust washer sliding under and particularly radially past the needle roller spacer which can produce problems later in the universal joint assembly. During assembly of the universal joint, a thrust washer separate from the needle roller spacer can fall out of the bearing entirely during handling of the bearing prior to its assembly into the arm of the yoke, which increases the possibility of early failure of the universal joint. To avoid these problems, additional vigilance is required during the manufacturing process, which ultimately increases the cost of the bearing assembly and of the universal joint assembly using the bearing assembly.
This problem had been recognized in the art and U.S. Pat. No. 5,106,342 shows one attempted solution. The thrust washer and needle roller spacer have a somewhat symmetrical thickness. There are connection tabs between the thrust washer and the needle spacer. Those tabs are deformable during installation of the combination and the trunnion in the combination to allow axial displacement of the thrust washer along the axis of the cup or the trunnion and that axial displacement is relevant to the needle roller displacement. Fracture of the tabs is a disclosed alternative.
However, this prior art system has drawbacks. Both antireversal capability and deformation of the connection tabs for relative axial displacement of the components requires a symmetric placement of the first washer thickness relative to the needle spacer thickness. This design symmetry may not allow for predictable and complete fracture of all of the connection tabs, if separation of the thrust washer from the spacer is required. If the thrust washer instead separates from the needle roller spacer prior to assembly of the universal joint, the thrust washer can fall out of the bearing assembly.
Connection tabs between the spacer and the thrust washer are likely to fracture during the assembly and particularly during insertion of the trunnion into the bearing cup. At fracture, connection tab fragments remain on one or both previously joined components. The location of the connection tab remnants after the fracture is not predictable if and when the thrust washer separates from the needle roller spacer. These fragments can result in possible interference by the tab remnants with the universal joint and with the trunnion. Further, if the thrust washer separates from the needle roller spacer during assembly of the bearing, the thrust washer could still slide under the needle roller spacer.